Catheters, particularly intravenous (IV) catheters, are used for directing fluid into or withdrawing fluid from a patient. The most common type of IV catheter is an over-the-needle IV catheter. As its name implies, an over-the-needle IV catheter is mounted over an introducer needle having a sharp distal tip. With the distal tip of the introducer needle extending beyond the distal tip of the IV catheter, the assembly is inserted through the patient's skin into a vein. Once placement of the assembly in the vein is verified by flashback of blood in the needle, the needle is withdrawn, leaving the IV catheter in place. In certain circumstances, the caregiver may move the needle within the vein, or may displace the catheter with respect to the needle, to locate the catheter in a desired position before fully withdrawing the needle. The proximal end of the IV catheter typically has a hub that is designed to be connectable to an IV fluid supply line after insertion of the IV catheter in a patient. In other applications, an IV set (known as an “extension set”) is attached before insertion into the patient.
Although typical IV catheter and introducer needle assemblies generally perform their functions satisfactorily, they do have certain drawbacks. For example, certain IV catheter and introducer needle assemblies typically require a flashback chamber located on the proximal end of the needle. This location is inconvenient for the healthcare worker because, during insertion of the assembly into a patient, the healthcare worker's attention is directed to the distal tip of the needle. Thus, in order to determine if the needle is properly placed in a vein, the healthcare worker has to divert his attention away from the point of insertion of the IV catheter and introducer needle assembly into the patient. Even in devices that permit visual confirmation of flashback at a location near the needle tip, there is no distinct confirmation that the needle remains in the vein as it is positioned by the caregiver. Typically, flashback chambers are immediately filled with blood upon the initial access of the vein and cannot be used to confirm that the catheter assembly has maintained (or achieved again) access to the vein.